(1) Field of the Invention
The present invention relates to an anti-crash seat and in particular a seat for a vehicle such as an aircraft. The seat incorporates means for protecting passengers in the event of violent impacts and/or a sudden change in the speed of the aircraft, in particular in the event of a crash.
(2) Description of Related Art
In a common embodiment, the seat associates a frame and a seat bucket that is made up of a seat proper with a seatback extending upwards therefrom. The frame is anchored to a floor of the aircraft via bottom brackets and it includes upright legs extending in elevation that are secured to the brackets and that together carry the bucket.
The term “bucket” is used to mean an assembly on which one or more passengers can sit. The bucket may thus be a bench suitable for receiving a plurality of passengers. In addition, the term “passenger” is used to designate any individual on board the aircraft, and thus applies equally to a pilot and to a person being transported.
Seats for aircraft also incorporate energy absorber means for protecting passengers sitting on such seats in the event of a crash.
For example, Document US 2009/0267390 proposes arranging at least one energy absorber element that is fastened to the bucket and to the frame. In the event of a crash, the bucket moves relative to the frame and thus deforms the absorber element. Deformation of the absorber element tends to dissipate at least a portion of the energy resulting from the crash.
The energy absorber means thus serve in particular to reduce the forces exerted on the lumbar vertebrae of a passenger in the event of a crash.
Certain civilian and military standards specify a weight population range for which a crash should be survivable, e.g. a range extending from a passenger weighing 46.5 kilograms (kg) to a passenger weighing 96 kg. The ability of the bone structure of a passenger to withstand an intense compression force, e.g. resulting from a sudden deceleration, varies significantly over this population range.
This range can make it difficult to determine the dimensions of the energy absorber means.
For example, if the energy absorber means are dimensioned for a passenger of light weight, then a passenger of heavy weight runs the risk of being injured because the energy absorber means may come into abutment or break as a result of a crash. On the contrary, if the energy absorber means are dimensioned for a heavy passenger, then the absorber will be overdimensioned for a light passenger, and the energy resulting from the deceleration to which a light passenger is subjected runs the risk of not being well dissipated.
Under such circumstances, seats are provided with hydraulic, electronic, or manual systems for adapting them to the weight of the passenger.
Document FR 2 923 568 describes an energy absorber device including automatic and independent setting means that incorporate a hydraulic fluid throttling mechanism for controlling the flow of said fluid between a high pressure chamber and a low pressure chamber. The pressure that exists in the high pressure chamber is associated with the extent to which the hydraulic fluid is compressed by a load support moving. By way of example, the support may constitute a bucket and the load may represent one or more passengers.
Although effective, hydraulic systems can give rise to problems of leakage, in particular because of the variations in pressure and temperature that are to be observed onboard an aircraft during a flight.
Document US 2008/0156602 presents an electronic system including a controller that controls an energy absorber as a function of information coming from sensors.
The operation of an electronic system can turn out to be erratic during a crash, which by its very nature is destructive.
Document U.S. Pat. No. 4,509,621 describes a system that is manually adjustable. Likewise document U.S. Pat. No. 4,358,154 provides an energy absorber system that can be adjusted using a knob.
Certain known seats are thus fitted with manual adjustment systems in order to adapt the energy absorber means to the weight of a passenger, for example. Those systems require human intervention which might be forgotten or which might lead to a wrong adjustment. Those systems are also often heavy, bulky, and expensive.
Furthermore, on a rotorcraft, and in particular a helicopter, a seat is heavily stressed in terms of vibration. Under such circumstances, the seat proper of the seat is generally covered in a lining of foam for limiting vibratory stress.
Thus, the seat has both crash energy absorber means and antivibration means, i.e. foam. It can be understood that throughout the present description, the term “energy absorber means” is used to designate means suitable for absorbing the energy that results from a large acceleration or deceleration during a crash, specifically for the purpose of protecting the lumbar vertebrae of an individual, and the term “antivibration means” is used to designate means for avoiding transmitting vibration from the vehicle to said individual in order to improve comfort.
Although effective, if the antivibration means are stressed little by the weight of a passenger, the crash energy absorber means are activated only after the residual stroke of the vibration of the absorber means has been used up. In other words, at the instant of a crash, the individual moves by stressing the antivibration means, i.e. by flattening the foam. The individual is therefore subjected to an increase in speed before stressing the crash energy absorber means. During a crash, the movement in translation of the individual is stopped suddenly. This leads to a force peak on the lumbar vertebrae at the moment when the crash energy absorber means are stressed. In compliance with certification requirements and in particular with the regulation known by the name “FAR part 29” that is applicable to rotorcraft, the force peak is acceptable so long as it remains below a maximum peak.
Manufacturers thus take this maximum peak into consideration when dimensioning the foam, for example.
Document US 2011/0204685 proposes using an inhibitor system for inhibiting antivibration means at the moment of a crash.
Furthermore, Document U.S. Pat. No. 5,692,705 describes a bench carried by vertical supports with at least one energy absorber being arranged between the bench and a vertical support.
The aircraft also includes at least one additional absorber that can be coupled to the bench with the help of a coupling mechanism under the control of a harness.
Document U.S. Pat. No. 3,482,872 does not lie in the technical field of the invention. That document describes means for attaching a safety belt while allowing for manual adjustment.